Cartridge case head



May 25, 1965 A. A. MAYER ETAL 3,185,095

CARTRIDGE CASE HEAD Filed Feb. 15, 1963 2 Sheets-Sheet l INVENTORS n ALI-RED A. MAYER o CHARLES E M/LLER FIG-5 May 25, 1965 A. A. MAYER ETAL CARTRIDGE CASE HEAD 2 Sheets-Sheet 2 Filed Feb. 15, 1963 41 0 4,1 L Jgn mmam =5 .Q M a ,v x L Q Q Q G qu INVENTORS. ALFRED A. MAYER FIG 5 BY CHARLES E. MILLER A T TORNEV 3,185,095 EARTRIDGE CASE HEAD Alfred A. Mayer, West Haven, and Charles E. Miller, Hamden, Conn, assignors to Glin Mathieson Chemical (lorporation, a corporation of Virginia Filed Feb. 1963, Ser. No. 258,751 8 Ellaims. (Cl. 102-44) This invention relates to ammunition and more specifically to a primer mounting in the base of a resinous plastic shotgun cartridge or the like cartridge of similar head construction.

In shotgun shells of this type, a recognized problem is in the ignition by primer devices which suffer from the disadvantage of an imperfect mounting and gas seal as evidenced by dropped and/ or blown primers. The problem occurs in such cartridges especially where the whole base as well as the tubular side wall are integrally formed of resinous plastic material, such as polyethylene, either by injection molding or by other and more preferable types of formation such as disclosed in copending patent applications Serial No. 135,569, filed September 1, 1961, and Serial No. 171,729, filed February 7, 1962, now abandoned.

With certain polymeric materials and particularly olefinic polymers, for example, the inclusion in such cartridges of a metal head encasing the base is advantageous but does not avoid or solve the problem altogether because of the shrinkage properties and elastomeric behavior of these plastics in general. The mixed crystalline and amorphic character and lubricity of such plastic materials as well as the distortion and shrinkage encountered with heating, cooling, molding, and stressing of such materials frequently results in detachment of the primer from its 1nount ing in the hole in the base of the shell, in lamination of the plastic base, and in leakage of escaping gas upon firing.

By this invention, the primer is properly retained and gas leakage avoided at the primer hole by a gas pressure responsive construction fabricated by compressive deformation at the cartridge base to lock the primer in its hole against the gas pressure both detentively and pneumatically. This is done making in tension a concentric flexible thick ring about the primer and a relief groove in turn about the ring for applying explosion pressure to the ring. Spaced from and surrounding the inner end of the primer battery cup by the thickness of the contractile ring, the groove is an internal one extending as a recess into the plastic base to form an annular distendable sac in communication with the powder cavity of the cartridge case; it extends as deeply as the ring projects about the primer. Both recess and ring extend a distance designed to overlie at least a part of the laterally distortable medial portion of the sidewall of the metallic battery cup for developing a pressure responsive bond without upsetting either the anvil or the primer cup containing the mix, while the bond is under hoop tension.

The invention and the objects of providing a method of sealing a primer in a cartridge and of providing such an improved cartridge will be better understood from a description of various embodiments and the accompanying drawing wherein:

FIG. 1 shows in a side view in partial cross section an unfinished shotgun cartridge case in apparatus at an intermediate stage of manufacture for making one improved ice base adapted to seal a primer in the cartridge base according to one method;

FIG. 2 is a fragment of a view of a case similar to that of FIG. 1 but showing a case in different apparatus and a more advanced stage of manufacture of another embodiment of improvement in the base;

FIG. 3 is another fragmentary view in cross section showing the finished base made according to either FIG. 1 or FIG. 2 with a primer inserted in place at a later stage of manufacture;

FIG. 4 shows in a side view in partial cross section another unfinished shotgun cartridge case in modified apparatus at an intermediate stage of manufacture similar to that shown in FIG. 1 for making still another embodiment of improved cartridge according to still another method;

FIG. 5 is an enlarged side view of a whole finished shotgun cartridge made according to the apparatus and method of FIG. 4 and providing another embodiment of cartridge of preferred construction shown. in longitudinal cross section taken medially on an axial plane of the cartridge;

FIG. 6 is an enlarged fragmentary view of a portion of a cartridge of this invention showing the base after the cartridge has been fired one or more times; and

FIG. 7 is an enlarged elevational view of a typical shotgun shell primer shown in cross section.

As shown in FIGS. 3 and 4 and also in greater detail in FIG. 7, in shotgun shells and similar centerfire ammunition, ignition is by means of a primer 10, consisting typically of a flanged battery cup 1 having a chamber housing, an anvil 2 mounted therein diametrically, and a cap 3 closing one end of the chamber the other end of which is closed except for a flash hole 4 formed in the cup. The cap is forced into the flanged end of the cup and contains the sensitive priming mix 5 which upon ignition fires through hole 4 into the cartridge charge of smokeless powder as disclosed typically in US. Patent No. 1,006,828, granted to R. G. Clyne, and in US. Patent No. 1,438,779, granted to John M. Olin.

According to FIG. 1, a polyethylene shot shell body 11 consisting of a relatively thick base 12 and a tubular side wall 13 integral with the base is provided with a metal head 14 encasing the base and this assembly is placed in the cavity of a die 29 for fabrication in the caivty between a hunter 21 and a seal ring forming punch 22. Base 12 and head 14 are perforated much undersize at the primer hole 15. In the apparatus, bunter 21 is extended at the hunter pin 23, the distal end 24 of which is of reduced diameter compared to the normal size of the primer to be received, While the intermediate portion 25 is tapered between end 24 and the sizing enlargement 26, for sizing and reforming the outer metal lined end of primer hole 15 in proper relationship with respect to its final finish size and the central axis of the shell. Punch 22 has a clearance opening 27 for bunter pin end 24 and has about this opening an axially extending annular ridge 28 of generally square shape displaced outwardly from coacting bunter pin end 24. Ridge 28 extends axially beyond the convex punch tip 29 which is of a shape generally complementary to the mating concave inner surface of the shell body 11 at the base 12. Ridge 28 forms a projection not only ahead of the ridge surrounding tip but also ahead of annular interior shoulder 30, which in turn is disposed axially intermediate tip 2? and the annular crest 31 of 3 v the ridge 28. Both shoulder 30 and crest 31 are in a generally flat configuration transversely with respect to inner and outer cylindrical walls 32 and 33 of the ridge.

This is for maximum axial pressing of the polymer reforming it to the ring and groove as punch 22 is forced into the unfinished base 12.

Punch 22 is driven under suflicient pressure, from the position shown in FIG. 1, toward bunter 21 to form a deep annular dent in the base 12 compressing and extending polyethylene back around bunter pin 23, forming a contraction.

The result of this stage of operation, which is not shown, is a compressive reformation of the resinous plastic and its fiow lines in the base in the central zone around the primer opening 15 providing around the finished primed opening 35 what amounts to an extremely undersize ring or stacks of integral 0 rings of plastic material surrounded by a high pressure gas receiving groove, as shown in FIG. 3.

The result at this stage is, however, shown in connection with another embodiment of seal ring forming punch 42 shown at FIG. 2 forced all the way toward a bunter 41 having a modified bunter pin 43 of a conical, or prolate hemispheroidal, or the like convex shape for co-action with the frustoconical interior surface 52 of a punch ridge 4-8 protruding ahead of the convex tip 49 of punch 42 provided as before with the clearance opening 47.

As a result of the compressive action occurring in the cavity of die 20 of FIG. 2, the cartridge has a reformed base 112 carrying an inwardly tapering ring 56 of plastic material constituting in effect a series of undersize 0 rings becoming progressively more undersize toward the interior end of the ring protruding into the shell body. This is accompanied by an annular groove left when the ridge 48 is withdrawn from the seal body.

After removal from the apparatus, at this stage base 112 has an opening 45 which tapers more severly to considerably more undersize and has a ring 56 under more tension than the contraction, formed according to the apparatus of FIG. .1.

a :height exceeding the thickness of the ring which has a thickness of at least about .020 of an inch but not more thanabout 0.060 of an inch. For example, a ring 66 having an average thickness of about 0.040-0.045 of an inch extends axially at least about 0.060 of an inch from its root to its crown.

Preferably, either at the root or intermediate the root and crown, the ring is its thinnest so that at the outer wall 38 it is most contractible responsive to the pressure developed in groove 37. At the crown, ring 66 is its thickest and under most hoop tension. Outer wall 38 does not terminate in a thin lip at the crown; as a result wall 38 is nearly cylindrical, being slightly tapered or contracted away from the crown and the resultant forces of the high pressure gas acting on the ring are maximized for holding the primer and are minimized axially.

The embodiments made according to FIGS. 1 and 2 are both adapted for the subsequent insertion of the primer into either the opening or opening 45, respectively toprovide the finish primed shell base and head struc ture as shown generally in FIG. 3. Insertion of primer 10 deforms the undersize primer opening of the ring to conform the interior ring surface 35 to the primer. The

entire ring of plastic is stretched to form the tension ring 66 having the outward surface 38 facing into the groove or sac 37 which is in communication with the powder cavity of the shot shell having a final finished head structure 212 of 'FIG. 3.

Although the general configuration is as shown in FIG. 3 for both of these embodiments when finished, the embodiment according to FIG. 2 will have a ring structure 4 cantilevered from its root where it is somewhat thinner than the resulting distal crest of the ring of FIG. 1, but in the embodiment according to FIG. 2 the ring is in greater tension distally in the cantilevered ring than the ring according to FIG. 1.

In the finished shot shell case, the resulting base structure 212 having ring pressure groove 37 and resinous plastic resilient ring 66, both of adequate depth and exceeding the thickness of the ring provides a primer seal responsive to both continuous tension and the explosive pressure developed in the cartridge case upon ignition of the propellant. Within limits of permissible radial thickness, it is desired that tension be enhanced as the outer diameter of the ring is increased and as the inner diameter is decreased, especially when providing a ring of increasing thickness toward the crest of the ridge made by the ring around the primer.

Alternatively, fabrication may be as shown in FIG. 4 for reformation of the plastic directly about a primer positioned before application of pressure, in an undersized hole.

According to FIG. 4, in die 20 a modified flat-faced bunter 51 and modified punch 52 make improvement in the head structure 12 of shell body 11 with primer 10 inserted in the opening of base 12 and head 14 before the apparatus operates on the base 12. The flat face 53 of the.

bunter supports primer 10 axially as the ridge 58, extending ahead of the annular fiat shoulder 60 and the convex tip 59 as before, is driven into the plastic material. Similarly, the ridge has the fiat crest 61 and the outer cylindrical wall 63, but unlike the punch 22 of FIG. 1, ridge 53 has a slightly tapered inner wall 62 for development of more radially inward thrust on the plastic about the primer 10, the protruding inner end of which is cleared in punch bore 57.

In operation, the device of FIG. 4 makes not only a sealing ring as before but also provides a novel shape of the ring 77 shown in FIG. 5 including a deformation of the polyethylene into locking engagement with a mating depression 78 forming a positive detent further locking the primer into the base 313 of the finished shell as shown in FIG. 5. Ring 77, formed about the primer instead of about a pin, bulges into the caved-in part 78 of the primer 10 and also has an outer circumferential wall 79 in the pressure groove 80 for receiving the explosive pressure. Ring 77 is at all times in hoop tension and positively engaged about primer 10; upon ignition of the powder charge 91 the ring responds to the gas pressure and binds itself even more tightly to the primer.

In the fully loaded shell of FIG. 5, the cold formed plastic structure in base 312 at the primer 10 involves a ring 77 having in this embodiment a bulge into the primer as well as an outer wall 79 nearly axial for pressure receiving all the way from the ring root, which is about 0.045 of an inch wide radially at the bottom of recess 80, up to the flat crest, which is about 0.035 of an inch wide radially and is placed axially from the root by a distance, which may vary from about 0.060 of an inch to as much as about 0.120 of an inch.

In any embodiment, it is to be understood that the ratio of ring axial length to radial thickness is greater than one and may vary from about 0.l20"/0.020", or 6:1 to about .060"/0.050", or about 1.2:1.0. This, for one gauge of shell, for example is for a seal ring having an outer diam eter of about 0.310 of an inch initially and an inner diameter of about 0.220 of an inch initially at the contraction grally with the shell side wall by in-folding characterized by pie cut panels and axially extending folds between panels within a surrounding rim portion.

In operation the under cut and pressure responsive ring assembled under tension with the primer provides a leakproof base in cartridges the body of which is made of plastic materials and particularly in those having a sheet metallic head encasing the plastic shell base and its rim and coacting with the modified base to hold the primer in a way superior to any way heretofore tried. As a result firing of the shell does not impair the base in a way precluding reloading of the shell.

Upon firing of the improved shell of this invention, the groove and ring structure of all embodiments is believed to develop a pinch action on the fired primer 110. As shown in FIG. 6, in the fired shell 100, during firing the ring is further contracted about the primer flank and the tension grip of the ring is enhanced to produce a contraction or further contraction at 178. The fired shell may be reloaded because there still remains in base 412 a ring 97, albeit slightly deformed, having an outer surface 98 for reception of gas pressure in a surrounding pressure sac 99 for action on a reload primer of the type shown in FIG. 7, inserted after the fired primer is extracted.

What is claimed is:

1. A shotgun cartridge comprising a primer, and an axially extending cartridge body integral with a base of deformable thermoplastic material such as high density linear polyethylene and the like crystalline polymer having an undersize aperture through said base and receiving said primer, with frictional retention therein for forming with said base part of the enclosing surface of the cartridge cavity receiving an explosive propellent, said primer having a lateral portion intermediate its ends deformed inwardly, said thermoplastic material being formed at said surface adjacent said aperture to provide a coaxial ring and a coaxial groove in said base, said groove being separated from said primer by the thickness of said coaxial ring of said material contracted at the inner end of said aperture about said primer, said ring having a portion extending int-o said deformed lateral primer portion to retain said primer, said ring being shaped as a ridge, having a relat-ively thin root on said base and extending upwardly to a relatively thick surface crest between said groove and primer, said groove being in communication with said cavity for applying the gas pressure generated by said propellent radially inwardly against said ring thereby creating a gas seal at said aperture between said base and primer and increasing said retention of said primer in said base.

2. The cartridge of claim 1 including about the base a base-encasing sheet metal head having an aperture aligned with the base aperture and being frictionally engaged with the primer.

3. The method of making an ammunition cartridge comprising a tubular body and a base integral therewith formed of deformable resinous plastic material and provided with an undersize aperture through said base for receiving a primer with frictional retention in said base defining with said primer a part of the surface enclosing the cartridge cavity containing an explosive propellent, said method comprising (a) forcing a primer in said aperture to put material in said base adjacent said aperture in tension, said primer having a portion intermediate its ends deformable inwardly, (b) indenting said base to form a ring of said material indenting said primer at said portion and to form an annular groove surrounding said primer disposed in spaced relationship by the thickness of said ring extending inwardly between said groove and said primer opposite at least said intermediate portion of the primer, said ring being contracted on part of said primer fitting snugly in said aperture at least against said ring, said groove being in communication with said cavity for applying the gas pressure generated by ignition of said propellent inwardly against said ring thereby creating a gas seal between said base and primer and increasing said retention of said primer in said base.

4. The method of making an ammunition cartridge comprising a tubular body and a base integral therewith formed of deformable resinous plastic material and provided with an aperture through said base for receiving the primer in said base, said primer having a deformable portion intermediate its ends, said body, integral base, and primer defining the surface enclosing the cartridge cavity containing an explosive propellent, said method comprising (a) indenting said base around said aperture to form a ring of said material including a contraction of said aperture and an annular groove around said ring spaced from said aperture by the thickness of said ring extending axially between said groove and said aperture to a height in excess of said thickness for disposition opposite at least said intermediate portion, (b) forcing said primer in said aperture to put said material in said base adjacent said aperture in tension contracted about said primer fitting snugly in frictional retention at least against said ring, said groove being in communication with said cavity for applying the gas pressure generated by ignition of said propellent inwardly against said ring thereby creating a gas pressure responsive seal between said primer and increasing said retention.

5. The method of making a shotgun cartridge having a primer including an open-ended battery cup, an anvil diametrically mounted adjacent its inner end to define a transversely deformable intermediate portion of said cup, and a primed cap mounted in and closing the other end of the battery cup and having a tubular body and base integral therewith formed of a plastic such as linear high density polyethylene or the like polymer defining with said primer the surface enclosing the cartridge cavity containing an explosive propellant for generating high pressure upon ignition, comprising the steps of forming said base with a primer-receiving aperture and indenting said base by compression of said plastic in an annular area around said aperture to form an axially extending groove in communication with said cavity and a ring of said plastic tending to contract with respect to said aperture and extending in tension between said groove and primer for securing said primer with frictional retention in said base and place said primer under compression and said ring in tension and pressure-responsive relationship thereby maintaining a gas seal and said retention between said base and primer during ignition.

6. The method of claim 5 wherein the material is compressibly deformed to make the body and base and further compressibly deformed to make the groove and ring.

7. A shotgun cartridge comprising a primer, a tubular body and a base integral therewith of compressively deformable high strength plastic such as linear high density polyethylene or the like material, a sheet metal head encasing and fixed to said head, said base and head having aligned axial apertures receiving said primer, said material and primer defining an internal surface enclosing the cartridge cavity containing an explosive propellant, said base being indented at said surface to form a groove concentric With said primer and a thickness of from about 0.02 to about 0.06 of an inch of said material defining an axially extending ring rising from said indented base between said primer and groove and in tension about said primer to form a contractible part of said base aperture for sealing and retention of said primer, said primer having a sidewall portion intermediate its ends, said ring extending axially upwardly in contact with said primer sidewall to a height exceeding said thickness and terminating in a lip below the top of said primer, said groove being in communication with said cavity for applying the gas pressure generated by ignition of said propellant substantially all radially inwardly against said ring from said lip thereby adding a pressure-responsive gas seal between said base and primer and increasing said primer retention in said base and head at said portion.

8. The cartridge of claim 7 wherein said ring extends into the intermediate sidewall portion of the primer at an indentation before and after ignition. t

5 References Cited by the'Examiner 2,987,775 6/61 Albrecht 1855 8 FOREIGN PATENTS 1,128,191 10/56. France.

1,140,147 2/57 France. 1,193,324 4/59 France.

128,271 6/ 19 Great Britain.

SAMUEL FEINBERG, Primary Examiner BENJAMIN A. BORCHELT, Examiner. 

1. A SHOTGUN CARTRIDGE COMPRISING A PRIMER, AND AN AXIALLY EXTENDING CARTRIDGE BODY INTEGRAL WITH A BASE OF DEFORMABLE THERMOPLASTIC MATERIAL SUCH AS HIGH DENSITY LINEAR POLYETHYLENE AND THE LIKE CRYSTALLINE POLYMER HAVING AN UNDERSIZE APERTURE THROUGH SAID BASE AND RECEIVING SAID PRIMER, WITH FRICTIONAL RETENTION THEREIN FOR FORMING WITH SAID BASE PART OF THE ENCLOSING SURFACE OF THE CARTRIDGE CAVITY RECEIVING AN EXPLOSIVE PROPELLENT, SAID PRIMER HAVING A LATERAL PORTION INTERMEDIATE ITS ENDS DEFORMED INWARDLY, SAID THERMOPLASTIC MATERIAL BEING FORMED AT SAID SURFACE ADJACENT SAID APERTURE TO PROVIDE A COAXIAL RING AND A COAXIAL GROOVE IN SAID BASE, SAID GROOVE BEING SEPARATED FROM SAID PRIMER BY THE THICKNESS OF SAID COAXIAL RING OF SAID MATERIAL CONTRACTED AT THE INNER END OF SAID APERTURE ABOUT SAID PRIMER, SAID RING HAVING A PORTION EXTENDING INTO SAID DEFORMED LATERIAL PRIMER PORTION TO RETAIN SAID PRIMER, SAID RING BEING SHAPED AS A RIDGE, HAVING A RELATIVELY THIN ROOT ON SAID BASE AND EXTENDING UPWARDLY TO A RELATIVELY THICK SURFACE CREST BETWEEN SAID GROOVE AND PRIMER, SAID GROOVE BEING IN COMMUNICATION WITH SAID 